It's not that simple: it seems that the issue isn't that WhatsApp/Facebook have wilfully disregarded the subpoena, but rather that Brazil isn't happy with their assertions that the information requested doesn't exist. WhatsApp has previously stated publicly that they don't retain any messages once they're delivered; if this is true, it's not strictly that they aren't willing to comply (though this may also be true), it's that they can't comply.